Over recent years there has been an increasing concern that a decline in male fertility is occurring. Some fertility experts warn that we are entering into a “sperm crisis”, as studies suggest that sperm counts have been falling over several decades. However, critics argue that this is a difficult trend to accurately measure and subject to many variables.
A global decline in male fertility?
In one European study, researchers investigated changes in semen quality in Danish men between 1977 and 19951. Scientists were interested to ascertain if semen parameters where influenced by seasonal variations and over time. The analysis was based on semen samples provided my 1, 927 donor candidates. Semen volume, sperm count, concentration and motility were assessed.
Researchers found that sperm counts were higher in spring and lowest in summer. However, over the duration of the study, sperm motility decreased. Although additional studies are necessary, this research clearly demonstrated changes in sperm quality over time, plus seasonal variations. This suggests that testicular function is also influenced by season, similar to other mammals.
While seasonal variations in semen quality is an important fertility consideration, what’s more alarming are the changes over time. Annually, there is a decline in male fertility by 1.9% according to the results of a recent French study. The retrospective research analysed data collected at assisted reproductive technology (ART) clinics in France from between 1989 and 20052.
The study population consisted of 26, 609 men. During the study period there was a continuous and significant decline in sperm concentration (26.3 to 36.3%). The average decrease over the 17 year study period was 32.2%. Projections based on a 35 year old male suggested that sperm concentration declined from an average of 73.6 million/ml in 1989 to 49.9 million/ml in 2005. Researchers also noted a decrease in healthy sperm motility over the 17 year period.
Given the large sample size and robust statistical analysis, researchers concluded that this study could reflect the overall status of male fertility in France. There have been additional studies with similar findings in other countries3,4.
Is there research bias defining a decline in male fertility?
With male infertility a hot topic, claims that semen quality is declining globally has generated a lot of debate. There are shortfalls in the current research. Studies have focused only on developed countries, introducing a selection bias. There is also variation in semen sample criteria and the types of men participating in this research. The men involved in these studies are typically affluent, city dwellers. Rural, low-income men are not well-represented, neither are men from low-income countries.
Despite the failings of the current research, there are still important observations. Male fertility is not static. Semen parameters can deteriorate and are influenced by other factors, including changes in seasons. Based on current research, in some developed countries there is evidence of a steady decline in male fertility. The extent and seriousness of these observations are yet to be determined.
What is causing the decline in male fertility?
There have been many suggestions for the decline in sperm counts in developed countries. These include exposure to toxins in the environment through to tight underwear. However, no definitive cause(s) has been determined. Lifestyle factors are believed to play a major role.
Less exercise, excess weight gain, poor food choices, alcohol and tobacco use; these are just some of the factors that are proven to adversely impact fertility. The good news is that these negative influences can be addressed and positive changes can be made to improve fertility. Diet is a major influence on fertility. Ensuring the body has access to the right nutrients is essential to support healthy semen parameters.
- “Gyllenborg, J. et.al. (1999). Secular and seasonal changes in semen quality among young Danish men: a statistical analysis of semen samples from 1927 donor candidates during 1977-1995. International Journal of Andrology, Volume 22, Issue 1, (pp. 28-36).” ↩
- “Rolland, M. et.al. (2013). Decline in semen concentration and morphology in a sample of 26 609 men close to the general population between 1989 and 2005 in France. Reproductive Biology, Volume 28, Issue 2, (pp. 462-470)”. ↩
- “Carlsen, E. et.al. (1992). Evidence for decreasing quality of semen during past 50 years. British Medical Journal, Volume 305, Issue 6854, (pp. 609-13).” ↩
- “Jorgensen, N. et.al. (2011). Recent adverse trends in semen quality and testis cancer incidence among Finnish men. International Journal of Andrology, Volume 34, Issue 4(2), (pp. 37-48).” ↩